Nightmare Fuel / Digimon Universe: App Monsters

• At the end of the very first episode we have the first signs of something being... off about Yuujin.
• The massive levels of surveillance used through the entirety of the series has its fair share of unnerving implications.
• The last scene of episode 28.
• Some of the Appmon (especially Medicmon, Resshamon and Racemon) easily could have caused countless deaths had they not been defeated fast enough.
• The entirety of episode 37 is mostly dead serious with only a few short goofs. The Downer Ending of the episode is especially this, combined with Tear Jerker.
  • Knight/Cloud shows signs of borderline psychopathy.
  • Biomon is arguably the scariest part of the whole episode.
• Episode 38 has Leviathan actively trying to murder Den'emon in the flashback by hacking various devices, going from random cars to even medical equipment. The Black Comedy reaction from Den'emon kinda mellows it down, but still.
• After The Reveal in episode 47, everything about Yuujin becomes this. He's an AI created by Leviathan who was ordered to keep watch over Haru since the beginning. He acts human most of the time, but also will follow orders with no hesitation, as seen when he ordered Shutmon to heartlessly cut down Bootmon to take his Appmon chip. It's also possible the "14" in his serial # means that his body has been constantly upgraded to match that of growing boy, or he has a body for every age he would noticeable have to have grown as Haru has seemingly known him for a long time.
  • The next episode shows that he has bodies for every age, in order to match Haru's growth so he can watch over him for Leviathan without suspicion. Furthermore, it shows that Yuujin's personality is entirely based around pleasing Haru, as he'll answer exactly as would befit Haru's perfect protagonist image. He even cries because that's what Haru would expect, despite not changing his tone or facial expression at all, which itself is some impressive Nightmare Fuel.
  • Yuujin emotionless persona visiting the depressed Haru, and trying to kill him using Rebootmon, can be compared to when ADR-01 from Digimon Tamers reveals her true self and attacks Takato who also has hard time to believe that she is not the real Jeri.
  • Yuujin's scream of agony when Leviathan's body is destroyed may hint something darker, considering how weary and pained he looks to be, just for reaching Haru's place. Hajime then scans Yuujin's android body and finds out that, while Leviathan's influence on Yuujin has gone, most of his AI has been damaged, and just a little part of it that still works. This fact frightens Denemon, that Leviathan and Yuujin's connection is perhaps even deeper than just a programmer and its created program.
  • It's later explained by Leviathan's reveal that Yuujin is actually part of him, which doesn't only mean that Yuujin can't live without Leviathan. But also the frightening possibility that all physical damages Leviathan took from Gaiamon and the others, indifferently affected the innocent-all-along Yuujin. Haru might have unintentionally killed the friend he tried to save, sooner than he thought...
• Shutmon cutting down Bootmon in episode 47. Bootmon may be an Ultimate Appmon, but it's clear he has the mentality of a child, making the moment very much this.
• In episode 49, we get a good look on people being grinded into data. The screams of pain and terror really sell the horrific scene.
• Leviathan's humongous form it assumes after being Appliarized by Yuujin is a giant six-headed hydra.